1. Field of the Invention
The present invention relates to integrated fiber array and lens array assemblies used in optoelectronic light gathering systems, and particularly to such assemblies which require accurate matching between the fiber array and the lens array due to varying effective focal lengths of lenses of the lens array.
2. Description of Prior Art
Nowadays speed, bandwidth and scalability of optical interconnections are becoming more and more important in communications networks. Due to the increasing density of optical fibers, ultra high precision of two-dimensional multi-fiber array systems must be achieved. For instance, overall positional tolerances in optical switch light gathering systems should be maintained within xc2x12 xcexcm. This is particularly important when light beams are gathered by a fiber array from a lens array in an optical switch.
U.S. Pat. No. 5,241,612 discloses a multi-core optical connector comprising a first connector part and a second connector part. The first connector part has a fiber array, a refractive index matching plate for preventing diffusion of beams, and a lens array. The second connector part has a fiber array and a lens array. A diameter of each of parallel beams that may be emitted outwardly from the lens array of the second connector part is larger than a diameter of parallel beams that may be emitted outwardly from the lens array of the first connector part. The first connector part and the second connector part are optically coupled such that both lens arrays are opposed to each other. The multi-core optical connector provides good alignment between the two fiber arrays, and minimizes axial deviation and angular deviation that may occur between the two fiber arrays. However, the multi-core optical connector does not provide accurate optical alignment between the fiber array and the lens array, as explained below.
An optical entry point of each fiber of a fiber array should be accurately positioned to correspond to a focal point of the corresponding lens of the lens array. Each lens of a typical lens array has a different focal length, due to unavoidable manufacturing tolerances. However, the optical entry points of all fibers in a typical fiber array are substantially coplanar. Therefore, it is virtually impossible to accurately coincide the optical entry points of the fiber array with the focal points of the lens array. Referring to FIG. 1, a conventional optical assembly 2 includes a fiber array 3 and a lens array 4. The fiber array 3 has a plurality of optical fibers 5 arrayed in a holder 6. The lens array 4 is made from a block of silica material. An array of lenses 7 is formed on one side of the silica block, by etching and machining. When the lens array 4 is thus formed, variance in focal lengths among each of the lenses 7 unavoidably exists. Therefore, positions of the focal points of the lenses 7 are not coplanar. Thus the lens array 4 as formed cannot accurately transmit light to the fibers 5 of the fiber array 3. Similarly, the fibers 5 of the fiber array 3 cannot efficiently transmit light to the lens array 4.
In view of the above, an object of the present invention is to provide a fiber array in which each fiber can accurately receive transmitting light from each lens of a lens array.
Another object of the present invention is to provide a method for manufacturing a fiber array.
In order to achieve the objects set above, the present invention provides a fiber array, of which a position of each fiber is axially adjustable for exactly receiving transmitting light from a corresponding lens array. The fiber array comprises a plurality of ferrules each defining a channel for retaining a fiber therein. An annular groove is defined in each ferrule. A ring is engagingly received in the groove of the ferrule. A press plate defines a plurality of blind threaded apertures, and a plurality of posts corresponding to the blind threaded apertures. Each post abuts an end of the corresponding ferrule and is capable of axially moving by means of a tool and a wrench. A holder plate defines a plurality of through holes corresponding to the blind threaded apertures of the press plate for retaining the corresponding ferrules and is secured to the first plate. A plurality of springs are interposed between the corresponding rings and the holder plate, and opposite ends thereof respectively abuts against the rings and the holder plate.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: